I wrote a library in JavaScript and chose the ISC license for its terseness, permissibility and likeness to the MIT license.

I would like to add some conditions to my software to limit specific uses without introducing a verbose license. If I switch to MIT can I add my own specific conditions to the software? Is it possible for me to simply update the ISC license to add my own conditions?

Example condition: Wrappers for Magento, WordPress and Drupal upon request only.

With help from commenters and others in this thread I learned the Free Software Foundation calls this Noncopylefted free software and defines it like so:

Noncopylefted free software comes from the author with permission to redistribute and modify, and also to add additional restrictions to it.

According to the selected answer, this kind of software may not be considered "open" nor "free".

  • 4
    "Example condition: Wrappers for Magento, WordPress and Drupal upon request only." What does this mean? Jul 3, 2017 at 15:27
  • It essentially means anyone is allowed to use the software, but to request permission before wrapping the library into a plugin wrapper for a major existing CMS. Intent is to prevent large commercial orgs from slurping up innovation just because they can.
    – vhs
    Jul 4, 2017 at 9:14
  • 3
    Hi Josh. That would make your license incompatible with the Free Software Definition and the Open Source Definition - and therefore off-topic for this site. Jul 4, 2017 at 9:34
  • No @JoshH you didn't understand correctly the "and also to add additional restrictions to it" part. This states that any recipient can add restrictions to their derivative.
    – Zimm i48
    Jul 16, 2017 at 13:36
  • I should point out that if you have previously released your software under the (unmodified) ISC license, people are free to use that version as they wish with no additional restrictions. There would be virtually no chance to enforce your new restricted license upon the old versions in a court of law, since the users have very good evidence that you explicitly licensed the old version under the ISC.
    – Vortico
    Jul 17, 2017 at 2:51

1 Answer 1


You could base yourself on the ISC license to create a new license but you should call it differently. Adding conditions to an existing license while keeping the same name is only creating confusion and you should not be surprised then that people do not respect the additional conditions.

Furthermore you shouldn't use the term "open source" or "free software" to describe your code anymore as what you are describing (adding restrictions on the uses) is not something that is compatible with the open source and free software definitions.

Finally, be aware that juridic wording is a difficult art, so adding new terms without the advice of a lawyer may simply result in a license which is non-enforceable.

  • 1
    Then you might be interested by opensource.stackexchange.com/q/5558/5858
    – Zimm i48
    Jul 4, 2017 at 10:03
  • In fact the closest thing to what you are looking for that actually exists might be the Creative Commons series of license but they can be built by combining various options but they are not fully extensible.
    – Zimm i48
    Jul 4, 2017 at 14:20
  • Indeed, they are.
    – Zimm i48
    Jul 4, 2017 at 14:42
  • Having an ad lib area is obviously not going to work. But having a bank of predefined, acceptable uses in a "common form" to choose from seems to be the ticket.
    – vhs
    Jul 5, 2017 at 9:21
  • 2
    @JoshH Technically, modifying existing licenses and adding additional licenses are known as "crayon licenses" and have zero support and are extremely frowned upon, in addition to other potential issues they may introduce. I'd recommend reading this: opensource.stackexchange.com/questions/1445/…
    – Zizouz212
    Jul 16, 2017 at 0:13

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